The present invention is directed to a method and apparatus for guidance and actuation of a flat belt drive having an outer load carrying side and an inner driven side which is wetted and which is trained around a drive and idler rollers.
Such belt drives are used in tire test machines (DE-OS 31 05 163) and particularly in vehicle test stands or chassis dynamometers (DE-OS 30 40 355) designed as so-called flat track test stands.
Unlike chassis dynamometers having rollers closely spaced to one another, in the case of flat track test stands, the vehicles are not supported by the rollers of the dynamometer. Instead, the vehicle or component to be investigated is supported by its wheels which rest upon a drive belt wrapped around two rollers or sheaves. In order to assure that accurate measured values are obtained it is important to make the belt drive quite stiff in the area of tire contact. As disclosed in DE-OS 31 05 103, this is accomplished at the support arrangement for the drive belts of tire test machines, by means of a support arrangement located between the rollers about which the flat belt is trained. This arrangement is covered by a plate with holes out of which liquid emerges perpendicular to the transport direction of the belt drive. The liquid enters the gap between the flexible steel belt and the plate. With this mechanism friction between the steel belt and the necessary support arrangement is reduced to a minimum, and additionally a stiff guidance is provided for the drive belt in the area of the tire contact of the wheel to be investigated.
Liquid between the idler and drive rollers and the steel band with the load thereon causes reduction of friction and impairment of guidance. In order to prevent the formation of a liquid layer at the steel band which would act as a layer between the band and the idler and the drive rollers, a wiper of synthetic material is arranged at the end of the support arrangement as viewed in the transport direction.
In order not to unreasonably shorten the life of the steel belts which are subject to constant bending around the drive and idler means it is necessary to employ large rollers for such belt drives. Further, belt drives with such rollers have the disadvantage of requiring considerable space. Their large mass is especially disadvantageous if, by means of such an arrangement, movements in the vertical direction are to be transmitted to the vehicle wheels.
In above mentioned DE-OS 30 40 355 a test stand is disclosed for the determination of the fatigue strength of motor cars or chassis components by means of a simulation of service loads. The wheels of the motor car or chassis components to be tested are supported by a roller element that is capable of either driving or braking. A separate roller element is coordinated to each wheel, and the positions of those roller elements are adjustable and independent of the position of the other roller elements. The roller elements in this case consist of linked belts that revolve over a load carrying plate between toothed deflection drives. An arrangement of this kind is not suitable for investigation at high speed where considerable forces are exerted because of the high wear rate of the metal parts used.